The present invention relates to apparatus for the automatic analysis of stereoscopic images together with the determination of the maximum degree of correlation of two similar images from the same object projected by two objectives, for instance for a range finder. The two images in the apparatus are superimposed on one or two spatial frequency filters indentical in their structures, and each particular supermposition signal generated preferably is applied to a particular photoelectric detector and the output signals of these photoelectric detectors are used for display and/or control purposes.
It is known to construct binocular rangefinders so as to eliminate any mechanical assembly changes possibly leading to spurious measurement results. According to this method of construction, a biaxial collimator is used with the help of which two illuminating indexes are projected into both beams in the direction of the incident object beam, the relative position of which with reference to the image position of the object is determined by means of oculars and compared by same.
German published application No. 2,158,761 and application Ser. No. 480,825 disclose a binocular rangefinder with optical correlator in which the two measurment beams comprising the object radiation are guided either to common or each separately to a measurement structure for instance a grating on which they produce the object images. The light fluxes obtained from the interaction of the images with the measurement structure when there is relative motion between this structure and the images are converted by means of a photoelectric receiver system electrical signals the properties of which are a measure of the particular distance between the object and the rangefinder. They are used for display and/or control.
Prior art practice has shown that given the same base line, the apparatus of application Ser. No. 480,825 is more accurate then those of prior art, but only if the above-mentioned mechanical changes, for instance due to temperature variations, do not occur or are eliminated. The above-described visual biaxial collimator cannot be used together with an instrument comprising an optical correlator because it assumes the comparison of the relative positions of two intangible (virtual) images, such comparison however being absent in an optical correlator. Latter always presupposes the presence of a tangible (real) image besides the presence of a concrete structure for the measurement of relative positions.